JPH03289455A - Inner separating sheet for food container and food packaging structure - Google Patents

Abstract

PURPOSE:To obtain an inner separating sheet capable of preventing the taste of food from being worsened due to the condensation taking place on the inner wall of a container by a method wherein a laminate structure is formed of a hydrophobic sheet and a cushioning layer and said structure is provided with a water resistance and a gas permeability, each being not lees than the specific value. CONSTITUTION:A sheet having a hydrophobic sheet and a cushioning layer built up in layers and a water resistance of at least 5cm and a gas permeability of at least 10cc/cm<2>/sec is placed under the bottom of food and/or on the top thereof with the hydrophobic sheet side in contact with the food. It is preferable, in the manufacture of the hydrophobic sheet, to use a melt blow nonwoven fabric made from polyolefin resin such as polyethylene and polypropylene, capable of meeting the above-mentioned requirements of the water resistance and gas permeability and having an average fiber size of at least 10mu in diameter and a unit weight of 3-50g/m<2> preferably 5-30g/m<2>.

Description

[Detailed description of the invention] [Industrial application field]

TECHNICAL FIELD The present invention relates to an insole sheet and a packaging structure using the insole sheet for preventing deterioration of the taste of the food due to dew condensation on the inner wall surface of the container when packaging foods such as folded lunch boxes and shumai.

[Conventional technology]

In recent years, along with the rise of the restaurant industry, demand for folded bento boxes and retort food has been rapidly increasing. Furthermore, the restaurant industry is becoming increasingly chain-based, and food products that require special skills to prepare, such as sushi rice, are prepared in bulk at centers and then delivered in the required quantities to chain restaurants. However, folded lunch boxes and sushi rice are generally packaged in containers while still warm, so dew condensation occurs inside the container due to the drop in temperature during transportation and storage, and the condensed water droplets are localized on the surface of the rice, shumai, etc. It is reabsorbed, leaving the food soggy and significantly reducing its taste. Conventionally, when packaging food products that produce drips, such as fish or meat, it has been proposed in Japanese Patent Application Laid-Open No. 2003-121013 to wrap the food by placing a perforated film or a drip-absorbing sheet that combines a water-permeable sheet and a water-absorbing layer on the bottom of the packaging container. 2-57582, JP 2-57583, JP 2-6054
This is proposed in Publication No. 2, etc. However, there is no known method to prevent condensation from forming on the inner surface of a folded lunch box due to temperature changes on the container wall, or to prevent condensed water droplets from being reabsorbed into the food and reducing its taste.

[Problem to be solved by the invention]

The present invention prevents moisture contained in food stored in a container from condensing inside the container due to temperature changes, and the condensed water droplets coming into contact with the surface of the food and being reabsorbed, resulting in a partially soggy state and deterioration of taste. The present invention provides a method for doing so, and an insole sheet for food containers used for that purpose.

[Means to solve the problem]

The present invention is a sheet formed by laminating a hydrophobic sheet and a buffer layer, which has a water resistance of 5 cm or more and an air permeability of 10 cc.
This is an insole sheet for a food container characterized by having a thickness of /am'/sea or more. The present invention also provides food packaging in which food is stored in a non-water-absorbing container, in which a hydrophobic sheet and a buffer layer are laminated on the bottom and/or top surface of the food, and the water resistance is 5 cm or more and the air permeability is 10 cc. This is a food packaging structure characterized in that a sheet having a diameter of /ca+''/sec or more is arranged so that the hydrophobic sheet side is in contact with the food.

[Effect]

The food container insole sheet of the present invention is composed of at least two layers: a waterproof hydrophobic sheet and a buffer layer, and the hydrophobic sheet is used on the side that comes into contact with the food.The laminated sheet has a water resistance of JIS L. - At least 5 cm using 1092A method
, preferably 10 cm and has an air permeability of JIS L-
1096A method is used with a velocity of 10 cc/cm"/sec or more, preferably 20 cc/cm"/sec or more. If the air permeability is lower than this value, the water vapor emitted by the food cannot be sufficiently diffused to the buffer layer side, resulting in a moist surface of the food. In addition, if the water resistance is low, water droplets condensed on the inner wall surface of the container return to the food side and wet the food surface, which is not preferable. For example, if a waterproof hydrophobic sheet is not laminated and only a buffer layer with virtually zero water resistance is used, foods such as rice and shumai will absorb condensed water and be directly exposed to the wet buffer layer. Because of the contact, the surface is always wet and locally reabsorbs moisture, resulting in a soggy state, which significantly impairs the taste. The buffer layer is necessary to prevent the hydrophobic sheet from directly contacting the container wall surface and being cooled, and to secure a space for the water vapor emitted by the food to diffuse to the outside through the hydrophobic sheet. The buffer layer also has the effect of retaining condensed moisture and preventing it from returning to the food. The hydrophobic sheet used on the side that comes into contact with food may be of any material, such as perforated film or fibrous sheet, as long as it satisfies water resistance and breathability; However, if the holes are formed by needle punching or the like, if the hole spacing is wide, dew condensation is likely to occur in the areas without holes, which is not preferable. In this respect, a fibrous sheet is preferable because it has an average air permeability throughout the sheet and does not cause dew condensation on the inner surface. In particular, from the viewpoint of food safety, fibers with an average fiber diameter of 10μ or less and a basis weight of 3 to 50 g/mz, preferably 5 to 30 g, can satisfy water resistance and air permeability without using additives or processing agents. /m
Melt-blown nonwoven fabrics made of polyolefin resins such as polyethylene and polyglopylene are preferably used. When used for folding or lunch boxes and heating the container in the microwave, polypropylene is more preferable because of its high melting point from the viewpoint of heat resistance. If it is less than 50g/m2, sufficient water resistance will not be obtained, and if it is more than 50g/m2, vapor permeability will be low. The buffer layer prevents the hydrophobic sheet from directly contacting the inner wall of the container and being cooled, and also provides space for the water vapor emitted by the food to permeate through the hydrophobic sheet and diffuse, preventing it from being cooled and condensing on the inner surface of the container. It is used to retain moisture in the form of water droplets, and it can be of any shape, such as non-woven fabric, paper, or sponge with open cells, as long as it has breathability that allows water vapor to pass through. A material with high porosity is preferable in terms of properties and water retention. The material is not particularly selected, but hydrophilic nonwoven fabrics and sponges are preferred because they absorb and retain condensed water droplets even if they have a low basis weight, and hydrophobic nonwoven fabrics and sponges are preferable because the entire surface gets wet and has good insulation properties. It is preferable because it does not deteriorate. Particularly when placed between the food and the lid of a lunch box, a sheet made of hydrophilic material is preferable because it absorbs condensed water and the entire sheet sticks to the lid, and when the lid is removed, the sheet is also removed at the same time. . From the point of view of safety for use in food products, it is best to use materials that do not contain additives or processing agents, such as spunpond nonwoven fabrics or high-Iharu 7' fibers that themselves have water absorption properties and moisture retention properties.
A nonwoven fabric manufactured by a dry method or a wet method using cellulose fibers such as regenerated cellulose fibers is preferred. When laminating with a hydrophobic sheet is carried out by heat melting, it is preferable to mix thermoplastic fibers with the cellulose fibers in order to improve adhesion. The basis weight when using a nonwoven fabric varies depending on its use, but it is generally in the range of 5 to 200 g/+a''.Those with a basis weight of 5 to 50 g/m'' are preferable for folding and lunch box inserts, and are 30 to 200 g/+a. m" is preferable as an insole for transporting large quantities of sushi rice etc. for commercial use. If the basis weight is less than 5 g/m", sufficient insulation, water retention, etc. buffering effects cannot be obtained; 200g
/m", there is no problem with the buffering effect, but the entire sheet becomes too thick and the quality is excessive, making it uneconomical. The hydrophobic sheet and the buffer layer are laminated and integrated to form an insole sheet. As a method, the whole may be lightly adhered by flat calendering as long as the air permeability is not impaired.
Alternatively, it may be partially bonded by methods such as hot embossing or ultrasonic bonding. Furthermore, adhesive may be used as long as food safety can be ensured. When partially adhering, the area of the first contact part is generally preferably in the range of 1 to 30% from the viewpoint of balancing breathability, strength, etc., but it varies depending on the basis weight of each sheet and is limited to this range. isn't it. From the point of view of the simplicity of the production process, the thermal bonding method is preferable because it allows continuous processing of long items using simple equipment. The insole sheet of the present invention can be used to store bento boxes such as station bentos, take-out bentos, and homemade bentos, as well as various foods such as pizza pie, gyoza, shumai, meat buns, red bean paste buns, hamburger pancakes, fried chicken, and sushi, in folded boxes that do not absorb water. By arranging the hydrophobic sheet below and/or above the food so that the side of the hydrophobic sheet is in contact with the food, it is possible to prevent these foods, such as cooked rice, from becoming soggy due to condensed water. Furthermore, since the insole sheet of the present invention does not allow liquid moisture to pass through, even if a juicy food is added to a lunch box as a side dish, the moisture will not be absorbed and removed by the buffer layer. When shipping or storing a large amount of sushi rice, etc. in a container, place the insole sheet of the present invention on the top and bottom surfaces of the container, preferably including the surrounding area, with the hydrophobic sheet side facing the food. By using this, it is possible to prevent sushi rice from becoming soggy due to moisture condensing on the inner surface of the container, and to keep it delicious for a long time. Condensation can be similarly prevented when storing in a heat insulating jar. [Examples] Further, the present invention will be explained by specific examples. Example 11 Comparative Example 1 An ultrafine fiber nonwoven fabric with an average fiber diameter of 3μ and a basis weight of 10g/m2 obtained by melt blowing polypropylene and a nonwoven fabric with a basis weight of 20g/m2 obtained by processing wood pulp using a papermaking method were laminated and pinpoint embossed. By doing this, a laminated sheet was made.The area of the adhesive part by embossing was about 5%, the water resistance was locm, and the air permeability was 25cc/cm'/
It was see. This laminated sheet was placed on the bottom of a bento box with the melt-blown non-woven fabric side facing up, hot rice and side dishes such as tempura were stuffed, and then the same sheet was placed on top with the melt-blown non-woven fabric side facing down and the lid was placed. For comparison, a lunch box was packed and covered in the same manner except that the sheet was not used. When I ate the bento 5 hours later, I found that although the bento using the insole sheet of the present invention was cold, the rice had a crispy texture, and the tempura batter remained crispy. On the other hand, for bento boxes that did not use an insole sheet, the part of the rice that was in contact with the lid and bottom of the bento box was soaking wet and soggy, and the batter on the tempura was also damp and tasteless. Example 2, Comparative Example 2 A heat-sealed nonwoven fabric with a basis weight of 150 g/m2 made of 60% rayon, 40% binder fibers with polyester as a core component and polyethylene as a sheath component was added to the melt-blown nonwoven fabric of Example 1 at intervals of 20 mm. Composite sheet binding by laminating with striped embossing. The above composite sheet was placed in a heat insulating jar with a volume of 10 liters so that the melt-blown nonwoven fabric was on the inside, warm sushi rice was added, the composite sheet was similarly placed on top, and the jar was left for 3 hours. For comparison, sushi rice was placed in a thermos jar and left in the same manner without using the composite sheet. When the sheet of the present invention was used, no deterioration of the quality of the sushi rice was observed, but when the sheet was not used, the top of the sushi rice and the part that was in contact with the container were wet and soggy when used for sushi. It wasn't possible. [Effects of the invention] By using the insole sheet of the present invention, bento boxes such as ekiben, take-out bento, and handmade bento packed in folding boxes, pizza bai, gyoza, shumai, nikuman, red bean paste, and non burger can be used. To prevent various foods such as pancakes, fried chicken, and sushi from becoming soggy due to condensed water for a long time, and to maintain good taste. Furthermore, since the insole sheet of the present invention does not allow liquid moisture to pass through, even if a juicy food is added to a lunch box as a side dish, the moisture will not be absorbed and removed by the buffer layer. Furthermore, even when a large amount of sushi rice, etc. is delivered or stored in a container such as a thermal jar, the sushi rice, etc. can be prevented from becoming soggy due to moisture condensing on the inner surface of the container, and can be kept delicious for a long time.

Claims (2)

[Claims] (1) A sheet made by laminating a hydrophobic sheet and a buffer layer, with a water resistance of 5 cm or more and an air permeability of 10 cc/c
An insole sheet for a food container, characterized in that it has a velocity of m^2/sec or more. (2) Food packaging in which food is stored in a non-water-absorbing container, in which a hydrophobic sheet and a buffer layer are laminated on the bottom and/or top surface of the food, has a water resistance of 5 cm or more and an air permeability of 1.
A food packaging structure characterized in that a sheet of 0 cc/cm^2/sec or more is arranged so that the hydrophobic sheet side is in contact with the food.